It's ambiguous because our knowledge is ambiguous. The definition you found is exactly the definition people use - i.e. a non-specific one. The HN audience skew

It's ambiguous because our knowledge is ambiguous. The definition you found is exactly the definition people use - i.e. a non-specific one. The HN audience skews toward engineer-brain, where there are only two classifications: Well defined and not well defined. But in most contexts, that's unrealistic. The author's opinion can be useful and possibly true even without needing to know exactly what subset of "processed" is bad, in what degrees, in which contexts, etc etc. That knowledge is a goal, and is useless as prerequisite. This happens all the time. "Chemicals", "organic", "natural", "processed", "additives". In the context of food, these words have no concrete meanings (though 'organic' has some regulatory definition sometimes), but they do have colloquial meanings. Sometimes people use them vaguely because they don't have strong knowledge on the topic, and sometimes they use them to refer to something more real. For example: "I think the fewer additives in foods and the less processed foods that we eat, the better off we will all be." This sentence sounds vague, but it might be absolutely true. Not everything you might call "additives"/"processing" is bad, but some of it is! It's reasonable to believe that, on average, the things most people would consider "additives"/"processing", have some deleterious effects.